畢業(yè)設(shè)計論文-外文文獻(xiàn)翻譯-橋梁專業(yè)-翻譯

PAGEPAGE24附錄一英文翻譯原文AUTOMATICDEFLECTIONANDTEMPERATUREMONITORINGOFABALANCEDCANTILEVERCONCRETEBRIDGEbyOlivierBURDET,Ph.D.SwissFederalInstituteofTechnology,Lausanne,SwitzerlandInstituteofReinforcedandPrestressedConcreteSUMMARYThereisaneedforreliablemonitoringsystemstofollowtheevolutionofthebehaviorofstructuresovertime.Deflectionsandrotationsarevaluesthatreflecttheoverallstructurebehavior.Thispaperpresentsaninnovativeapproachtothemeasurementoflong-termdeformationsofbridgesbyuseofinclinometers.Highprecisionelectronicinclinometerscanbeusedtofolloweffectivelylong-termrotationswithoutdisruptionofthetraffic.Inadditiontotheiraccuracy,theseinstrumentshaveproventobesufficientlystableovertimeandreliableforfieldconditions.TheMentuebridgesaretwin565mlongbox-girderpost-tensionedconcretehighwaybridgesunderconstructioninSwitzerland.Thebridgesarebuiltbythebalancedcantilevermethodoveradeepvalley.Thepiersare100mhighandthemainspanis150m.Acentralizeddataacquisitionsystemwasinstalledinonebridgeduringitsconstructionin1997.Everyminute,thesystemrecordstherotationandtemperatureatanumberofmeasuringpoints.Thesimultaneousmeasurementofrotationsandconcretetemperatureatseverallocationsgivesaclearideaofthemovementsinducedbythermalconditions.Thesystemwillbeusedincombinationwithahydrostaticlevelingsetuptofollowthelong-termbehaviorofthebridge.Preliminaryresultsshowthatthesystemperformsreliablyandthattheaccuracyofthesensorsisexcellent.Comparisonoftheevolutionofrotationsandtemperatureindicatethatthestructurerespondstochangesinairtemperatureratherquickly.BACKGROUNDAllovertheworld,thenumberofstructuresinservicekeepsincreasing.Withthedevelopmentoftrafficandtheincreaseddependenceonreliabletransportation,itisbecomingmoreandmorenecessarytoforeseeandanticipatethedeteriorationofstructures.Inparticular,forstructuresthatarepartofmajortransportationsystems,rehabilitationworksneedtobecarefullyplannedinordertominimizedisruptionsoftraffic.Automaticmonitoringofstructuresisthusrapidlydeveloping.Long-termmonitoringofbridgesisanimportantpartofthisoverallefforttoattempttominimizeboththeimpactandthecostofmaintenanceandrehabilitationworkofmajorstructures.Byknowingtherateofdeteriorationofagivenstructure,theengineerisabletoanticipateandadequatelydefinethetimingofrequiredinterventions.Conversely,interventionscanbedelayeduntiltheconditionofthestructurerequiresthem,withoutreducingtheoverallsafetyofthestructure.Thepaperpresentsaninnovativeapproachtothemeasurementoflong-termbridgedeformations.Theuseofhighprecisioninclinometerspermitsaneffective,accurateandunobtrusivefollowingofthelong-termrotations.Themeasurementscanbeperformedundertrafficconditions.Simultaneousmeasurementofthetemperatureatseverallocationsgivesaclearideaofthemovementsinducedbythermalconditionsandthoseinducedbycreepandshrinkage.ThesystempresentedisoperationalsinceAugust1997intheMentuebridge,currentlyunderconstructioninSwitzerland.Thestructurehasamainspanof150mandpiers100mhigh.2.LONG-TERMMONITORINGOFBRIDGESAspartofitsresearchandserviceactivitieswithintheSwissFederalInstituteofTechnologyinLausanne(EPFL),IBAP-ReinforcedandPrestressedConcretehasbeeninvolvedinthemonitoringoflong-timedeformationsofbridgesandotherstructuresforovertwenty-fiveyears[1,2,3,4].Inthepast,IBAPhasdevelopedasystemforthemeasurementoflong-termdeformationsusinghydrostaticleveling[5,6].ThissystemhasbeeninsuccessfulserviceintenbridgesinSwitzerlandforapproximatelytenyears[5,7].Thesystemisrobust,reliableandsufficientlyaccurate,butitrequireshumaninterventionforeachmeasurement,andisnotwellsuitedforautomaticdataacquisition.Oneadditionaldisadvantageofthissystemisthatitisonlyeasilyapplicabletoboxgirderbridgeswithanaccessiblebox.Occasionalcontinuousmeasurementsoverperiodsof24hourshaveshownthattheamplitudeofdailymovementsissignificant,usuallyamountingtoseveralmillimetersoveracoupleofhours.Thisisexemplifiedinfigure1,wheremeasurementsofthetwinLutrivebridges,takenoveraperiodofseveralyearsbeforeandaftertheywerestrengthenedbypost-tensioning,areshownalongwithmeasurementsperformedoveraperiodof24hours.Thescatterobservedinthedataisprimarilycausedbythermaleffectsonthebridges.Inthecaseofthesebox-girderbridgesbuiltbythebalancedcantilevermethod,withamainspanof143.5m,theamplitudeofdeformationsonasunnydayisofthesameorderofmagnitudethanthelongtermdeformationoverseveralyears.Instantaneousmeasurements,asthosemadebyhydrostaticleveling,arenotnecessarilyrepresentativeofthemeanpositionofthebridge.Thisoccursbecausethepositionofthebridgeatthetimeofthemeasurementisinfluencedbythetemperaturehistoryoverthepastseveralhoursanddays.Evenifeverycarewastakentoperformthemeasurementsearlyinthemorningandatthesameperiodeveryyear,ittookarelativelylongtimebeforeitwasrealizedthattheretrofitperformedontheLutrivebridgesin1988byadditionalpost-tensioning[3,7,11]hadnothadthesameeffectonbothofthem.Figure1:Long-termdeflectionsoftheLutrivebridges,comparedtodeflectionsmeasuredina24-hourperiodAutomaticdataacquisition,allowingfrequentmeasurementstobeperformedatanacceptablecost,isthushighlydesirable.Astudyofpossiblesolutionsincludinglaser-basedleveling,fiberopticssensorsandGPS-positioningwasperformed,withtheconclusionthat,providedthattheirlong-termstabilitycanbedemonstrated,currenttypesofelectronicinclinometersaresuitableforautomaticmeasurementsofrotationsinexistingbridges[8].3.MENTUEBRIDGESTheMentuebridgesaretwinbox-girderbridgesthatwillcarrythefutureA1motorwayfromLausannetoBern.Eachbridge,similarindesign,hasanoveralllengthofapproximately565m,andawidthof13.46m,designedtocarrytwolanesoftrafficandanemergencylane.Thebridgescrossadeepvalleywithsteepsides(fig.2).Thebalancedcantileverdesignresultsfromabridgecompetition.The100mhighconcretepierswerebuiltusingclimbingformwork,afterwhichtheconstructionofthebalancedcantileverstarted(fig.3).4.INCLINOMETERSStartingin1995,IBAPinitiatedaresearchprojectwiththegoalofinvestigatingthefeasibilityofameasurementsystemusinginclinometers.Preliminaryresultsindicatedthatinclinometersofferseveraladvantagesfortheautomaticmonitoringofstructures.Table1summarizesthemainpropertiesoftheinclinometersselectedforthisstudy.Oneinterestingpropertyofmeasuringastructure’srotations,isthat,foragivenratioofmaximumdeflectiontospanlength,themaximumrotationisessentiallyindependentfromitsstaticsystem[8].Sincemaximalallowablevaluesofabout1/1,000forlong-termdeflectionsunderpermanentloadsaregenerallyacceptedvaluesworldwide,developmentsmadeforbox-girderbridgeswithlongspans,asisthecaseforthisresearch,areapplicabletootherbridges,forinstancebridgeswithshorterspansandothertypesofcross-sections.Thisissignificantbecauseoftheneedtomonitorsmallerspanswhichconstitutethemajorityofallbridges.TheselectedinclinometersareoftypeWylerZerotronic±1°[9].Theiraccuracyis1microradian(μrad),whichcorrespondstoarotationofonemillimeterperkilometer,averysmallvalue.Foranintermediatespanofacontinuousbeamwithaconstantdepth,amid-spandeflectionof1/20,000wouldinduceamaximumrotationofabout150μrad,or0.15milliradians(mrad).Onepotentialproblemwithelectronicinstrumentsisthattheirmeasurementsmaydriftovertime.Toquantifyandcontrolthisproblem,amechanicaldevicewasdesignedallowingtheinclinometerstobepreciselyrotatedof180°inanhorizontalplane(fig.4).Thedriftofeachinclinometercanbeverysimplyobtainedbycomparingthevaluesobtainedintheinitialandrotatedpositionwithpreviouslyobtainedvalues.Sofar,ithasbeenobservedthatthetypeofinclinometerusedinthisprojectisnotverysensitivetodrifting.5.INSTRUMENTATIONOFTHEMENTUEBRIDGESBecauseanumberofbridgesbuiltbythebalancedcantilevermethodhaveshownanunsatisfactorybehaviorinservice[2,7,10],itwasdecidedtocarefullymonitortheevolutionofthedeformationsoftheMentuebridges.Thesebridgesweredesignedtakingintoconsiderationrecentrecommendationsforthechoiceoftheamountofposttensioning[7,10,13].Monitoringstartingduringtheconstructionin1997andwillbepursuedafterthebridgesareopenedtotrafficin2001.Deflectionmonitoringincludestopographiclevelingbythehighwayauthorities,anhydrostaticlevelingsystemovertheentirelengthofbothbridgesandanetworkofinclinometersinthemainspanoftheNorthbridge.Datacollectioniscoordinatedbytheengineerofrecord,tofacilitatecomparisonofmeasuredvalues.Theinformationgainedfromtheseobservationswillbeusedtofurtherenhancethedesigncriteriaforthattypeofbridge,especiallywithregardtotheamountofpost-tensioning[7,10,11,12,13].Theautomaticmonitoringsystemisdrivenbyadataacquisitionprogramthatgathersandstoresthedata.Thissystemisabletocontrolvarioustypesofsensorssimultaneously,atthepresenttimeinclinometersandthermalsensors.Thecomputerprogramdrivingalltheinstrumentationoffersaflexibleframework,allowingthelateradditionofnewsensorsordataacquisitionsystems.TheuseofthedevelopmentenvironmentLabView[14]allowedtoleveragethelargeuserbaseinthefieldoflaboratoryinstrumentationanddataanalysis.Thedataacquisitionsystemrunsonarathermodestcomputer,withanIntel486/66Mhzprocessor,16MBofmemoryanda500MBharddisk,runningWindowsNT.Allsensordataaregatheredonceperminuteandstoredincompressedformontheharddisk.Thesystemislocatedinthebox-girderontopofpier3(fig.5).Itcanwithstandsevereweatherconditionsandwillrestartitselfautomaticallyafterapoweroutage,whichhappenedfrequentlyduringconstruction.6.SENSORSFigure5(a)showsthelocationoftheinclinometersinthemainspanoftheNorthbridge.Thesensorsareplacedattheaxisofthesupports(①and⑤),at1/4and3/4(③and④)ofthespanandat1/8ofthespanfor②.Inthecrosssection,thesensorsarelocatedontheNorthweb,ataheightcorrespondingtothecenterofgravityofthesection(fig.5a).ThesensorsareallconnectedbyasingleRS-485cabletothecentraldataacquisitionsystemlocatedinthevicinityofinclinometer①.Monitoringofthebridgestartedalreadyduringitsconstruction.Inclinometers①,②and③wereinstalledbeforethespanwascompleted.Theresultingmeasurementweredifficulttointerpret,however,becauseofthewidevariationsofanglesinducedbythevariousstagesofthisparticularThedeflectedshapewillbedeterminedbyintegratingthemeasuredrotationsalongthelengthofthebridge(fig.5b).Althoughthisintegrationisinprinciplestraightforward,ithasbeenshown[8,16]thatthetypeofloadingandpossiblemeasurementerrorsneedtobecarefullytakenintoaccount.Thermalsensorswereembeddedinconcretesothattemperatureeffectscouldbetakenintoaccountfortheadjustmentofthegeometryoftheformworkforsubsequentcasts.Figure6showsthelayoutofthermalsensorsinthemainspan.Themeasurementsectionsarelocatedatthesamesectionsthantheinclinometers(fig.5).Allsensorswereplacedintheformworkbeforeconcretingandwereoperationalassoonastheformworkwasremoved,whichwasrequiredfortheneedsoftheconstruction.Ineachsection,sevenoftheninethermalsensor(indicatedinsolidblackinfig.6)arenowautomaticallymeasuredbythecentraldataacquisitionsystem.7.RESULTSFigure7showstheresultsofinclinometrymeasurementsperformedfromtheendofSeptembertothethirdweekofNovember1997.Allinclinometersperformedwellduringthatperiod.Occasionalinterruptionsofmeasurement,asobservedforexampleinearlyOctoberareduetointerruptionofpowertothesystemduringconstructionoperations.Theoverallsymmetryofresultsfrominclinometersseemtoindicatethattheinstrumentsdriftisnotsignificantforthattimeperiod.Themaximumamplitudeofbridgedeflectionduringtheobservedperiod,estimatedonthebasisoftheinclinometersresults,isaround40mm.Moreaccuratevalueswillbecomputedwhenthemethodofdeterminationofdeflectionswillhavebeenfurthercalibratedwithothermeasurements.Severalperiodsofincrease,respectivelydecrease,ofdeflectionsoverseveraldayscanbeobservedinthegraph.Thisfurtherillustratestheneedforcontinuousdeformationmonitoringtoaccountforsucheffects.Termsofconstruction,andincludedthefollowingoperations:thefinalconcretepoursinthatspan,horizontaljackingofthebridgetocompensatesomepiereccentricities,aswellasthestressingofthecontinuitypost-tensioning,andthede-tensioningoftheguycables(fig.3).Asaconsequence,theinterpretationofthesemeasurementsisquitedifficult.Itisexpectedthatfurthermeasurements,madeafterthecompletionofthebridge,willbesimplertointerpret.Figure8showsadetailofthemeasurementsmadeinNovember,whilefigure.9showstemperaturemeasurementsatthetopandbottomofthesectionatmid-spanmadeduringthatsameperiod.Itisclearthatthemeasureddeflectionscorrespondtochangesinthetemperature.Thetemperatureatthebottomofthesectionfollowscloselyvariationsoftheairtemperature(measuredintheshadenearthenorthwebofthegirder).Ontheotherhand,thetemperatureatthetopofthecrosssectionislesssubjecttorapidvariations.Thismaybeduetothehighelevationofthebridgeaboveground,andalsotothefactthat,duringthemeasuringperiod,therewaslittledirectsunshineonthedeck.Thetemperaturegradientbetweentopandbottomofthecrosssectionhasadirectrelationshipwithshort-termvariations.Itdoesnot,however,appeartoberelatedtothegeneraltendencytodecreaseinrotationsobservedinfig.8.8.FUTUREDEVELOPMENTSFuturedevelopmentswillincludealgorithmstoreconstructdeflectionsfrommeasuredrotations.Toenhancetheaccuracyofthereconstructionofdeflections,a3Dfiniteelementmodeloftheentirestructureisinpreparation[15].Thismodelwillbeusedtoidentifytheinfluenceonrotationsofvariousphenomena,suchascreepofthepiersandgirder,differentialsettlements,horizontalandverticaltemperaturegradientsortrafficloads.MuchworkwillbedevotedtotheinterpretationofthedatagatheredintheMentuebridge.Thefinalpartoftheresearchprojectworkwillfocusontwoaspects:understandingtheverycomplexbehaviorofthestructure,anddeterminingthemostimportantparameters,toallowasimpleandeffectivemonitoringofthebridgesdeflections.Finally,theresearchreportwillproposeguidelinesfordeterminationofdeflectionsfrommeasuredrotationsandpracticalrecommendationsfortheimplementationofmeasurementsystemsusinginclinometers.Itisexpectedthatwithinthecomingyearnewsiteswillbeequippedwithinclinometers.Experiencesmadebyusinginclinometerstomeasuredeflectionsduringloadingtests[16,17]haveshownthatthemethodisveryflexibleandcompetitivewithotherhigh-techmethods.Asanextensiontothecurrentresearchproject,aninnovativesystemforthemeasurementofbridgejointmovementisbeingdeveloped.Thissystemintegrateseasilywiththeexistingmonitoringsystem,becauseitalsousesinclinometers,althoughfromaslightlydifferenttype.9.CONCLUSIONSAninnovativemeasurementsystemfordeformationsofstructuresusinghighprecisioninclinometershasbeendeveloped.Thissystemcombinesahighaccuracywitharelativelysimpleimplementation.Preliminaryresultsareveryencouragingandindicatethattheuseofinclinometerstomonitorbridgedeformationsisafeasibleandoffersadvantages.Thesystemisreliable,doesnotobstructconstructionworkortrafficandisveryeasilyinstalled.Simultaneoustemperaturemeasurementshaveconfirmedtheimportanceoftemperaturevariationsonthebehaviorofstructuralconcretebridges.10.REFERENCES[1]ANDREYD.,Maintenancedesouvragesd’art:méthodologiedesurveillance,PhDDissertationNr679,EPFL,Lausanne,Switzerland,1987.[2]BURDETO.,LoadTestingandMonitoringofSwissBridges,CEBInformationBulletinNr219,SafetyandPerformanceConcepts,Lausanne,Switzerland,1993.[3]BURDETO.,Critèrespourlechoixdelaquantitédeprécontraintedécoulantdel.observationdepontsexistants,CUST-COS96,Clermont-Ferrand,France,1996.[4]HASSANM.,BURDETO.,FAVRER.,CombinationofUltrasonicMeasurementsandLoadTestsinBridgeEvaluation,5thInternationalConferenceonStructuralFaultsandRepair,Edinburgh,Scotland,UK,1993.[5]FAVRER.,CHARIFH.,MARKEYI.,Observationàlongtermedeladéformationdesponts,MandatdeRecherchedel’OFR86/88,FinalReport,EPFL,Lausanne,Switzerland,1990.[6]FAVRER.,MARKEYI.,Long-termMonitoringofBridgeDeformation,NATOResearchWorkshop,BridgeEvaluation,RepairandRehabilitation,NATOASIseriesE:vol.187,pp.85-100,Baltimore,USA,1990.[7]FAVRER.,BURDETO.etal.,Enseignementstirésd’essaisdechargeetd’observationsàlongtermepourl’évaluationdespontsetlechoixdelaprécontrainte,OFRReport,83/90,Zürich,Switzerland,1995.[8]DAVERIOR.,Mesuresdesdéformationsdespontsparunsystèmed’inclinométrie,Rapportdema?triseEPFL-IBAP,Lausanne,Switzerland,1995.[9]WYLERAG.,TechnicalspecificationsforZerotronicInclinometers,Winterthur,Switzerland,1996.[10]FAVRER.,MARKEYI.,GeneralizationoftheLoadBalancingMethod,12thFIPCongress,PrestressedConcreteinSwitzerland,pp.32-37,Washington,USA,1994.[11]FAVRER.,BURDETO.,CHARIFH.,Critèrespourlechoixd’uneprécontrainte:applicationaucasd’unrenforcement,"ColloqueInternationalGestiondesOuvragesd’Art:QuelleStratégiepourMainteniretAdapterlePatrimoine,pp.197-208,Paris,France,1994.[12]FAVRER.,BURDETO.,WahleinergeeignetenVorspannung,Beton-undStahlbetonbau,Beton-undStahlbetonbau,92/3,67,Germany,1997.[13]FAVRER.,BURDETO.,Choixd’unequantitéappropriéedeprécontrainte,SIAD0129,Zürich,Switzerland,1996.[14]NATIONALINSTRUMENTS,LabViewUser.sManual,Austin,USA,1996.[15]BOUBERGUIGA.,ROSSIERS.,FAVRER.etal,Calculnonlinéairedubétonarméetprécontraint,RevueFran?aisduGénieCivil,vol.1n°3,Hermes,Paris,France,1997.[16]FESTE.,Systèmedemesureparinclinométrie:développementd’unalgorithmedecalculdesflèches,Mémoiredema?trisedeDEA,Lausanne/Paris,Switzerland/France,1997.[17]PERREGAUXN.etal.,VerticalDisplacementofBridgesusingtheSOFOSystem:aFiberOpticMonitoringMethodforStructures,12thASCEEngineeringMechanicsConference,SanDiego,USA,tobepublished,1998.譯文平衡懸臂施工混凝土橋撓度和溫度的自動監(jiān)測

作者OlivierBURDET博士

瑞士聯(lián)邦理工學(xué)院，洛桑，瑞士

鋼筋和預(yù)應(yīng)力混凝土研究所

概要：我們想要跟蹤結(jié)構(gòu)行為隨時間的演化，需要一種可靠的監(jiān)測系統(tǒng)。撓度和旋轉(zhuǎn)兩個參數(shù)反映了結(jié)構(gòu)的整體行為。本文提出了一種測量橋梁長期變形的創(chuàng)新方法，即，使用傾角儀。高精密電子傾角儀可以有效地追蹤橋梁的長期旋轉(zhuǎn)而不需要中斷交通。除了準(zhǔn)確，這些儀器已被證明隨著時間的推移是足夠穩(wěn)定，野外條下也非?？煽?。

Mentue橋，長565m，雙箱雙室梁，后張法預(yù)應(yīng)力混凝土公路橋梁，修建于瑞士。該橋由平衡懸臂法修建于一條深谷之上。墩高100m，主跨為150m。一個集中的數(shù)據(jù)采集系統(tǒng)于1997年修建該橋時安裝在一梁上。每一分鐘，系統(tǒng)記錄了很多測量點的旋轉(zhuǎn)量和溫度值。在多個地點同時測量出的旋轉(zhuǎn)量和混凝土溫度給出了熱條件引起的變動的初步結(jié)果表明該系統(tǒng)運行可靠，并且傳感器的準(zhǔn)確性非常優(yōu)秀。

對旋轉(zhuǎn)和溫度的演變比較表明，結(jié)構(gòu)對氣溫變化的反應(yīng)相當(dāng)快。

1.背景

遍布世界，服役結(jié)構(gòu)的數(shù)量在不斷增加。隨著交通的發(fā)展，我們?nèi)找嬉蕾囉诳煽康慕煌ㄟ\輸，越來越有必要去預(yù)見和預(yù)測結(jié)構(gòu)的惡化。特別是，對于主要運輸系統(tǒng)的那部分結(jié)構(gòu)，修復(fù)工程需要認(rèn)真規(guī)劃，以盡量減少交通中斷。結(jié)構(gòu)自動監(jiān)測儀器從而迅速發(fā)展。

長期橋梁監(jiān)測是這一全面努力的重要組成部分，以嘗試減少對主要結(jié)構(gòu)的影響和維修工程的費用。通過了解某一特定結(jié)構(gòu)的惡化速度，工程師能夠預(yù)見并充分界定所要求的處理措施的時機(jī)。相反，不降低結(jié)構(gòu)的整體安全性，處理可以推遲到結(jié)構(gòu)需要相應(yīng)措施的時候。

本文提出了一種檢測橋梁長期變形的創(chuàng)新方法。高精度傾角儀的使用允許我們可以對長期旋轉(zhuǎn)進(jìn)行有效、準(zhǔn)確和無障礙跟蹤。該測量設(shè)備可以在正常交通狀況下運行。同一時間測量的、多個地點的溫度給出了一個由熱、蠕變和收縮導(dǎo)致的變形的清晰概念。提出該系統(tǒng)的可行性是1997年8月開始運營的修建于瑞士的Mentue橋。該橋主跨150m，墩高100m。

2.橋梁的長期監(jiān)測

作為其研究和瑞士聯(lián)邦理工學(xué)院（洛桑聯(lián)邦理工學(xué)院）服務(wù)活動的一部分，該橋梁和其他結(jié)構(gòu)涉及到的鋼筋混凝土和預(yù)應(yīng)力混凝土長期變形的監(jiān)測已超過二十五年[1，2，3，4]。在過去，IBAP已經(jīng)制定了一個長期變形測量的水準(zhǔn)測量系統(tǒng)[5，6]。該系統(tǒng)已成功的服務(wù)于瑞士的十座橋梁約十年[5,7]。該系統(tǒng)強(qiáng)大，可靠和足夠準(zhǔn)確，但它要求每次測量要人為操作，并沒有很好地適合于數(shù)據(jù)自動采集。該系統(tǒng)另外的一個缺點是，它只是較容易適用于可接觸到的箱形梁橋。

偶爾超過24小時的連續(xù)測量表明，它日常變形幅度很大，通常一兩個小時內(nèi)幾個毫米。這體現(xiàn)在圖1中，那里的雙箱雙室梁Lutrive橋在他們被后張之前和爾后超過數(shù)年的測量顯示了24小時內(nèi)的測量結(jié)果。觀察到的數(shù)據(jù)散射主要是由橋梁的熱效應(yīng)造成的。用平衡懸臂法建造、1435m主跨的箱形梁，在一個陽光明媚的日子變形幅度是與過去數(shù)年的長期變形屬于同一量級瞬時測量，如水準(zhǔn)測量得出的結(jié)果，不一定代表了該橋的平均位置。這是因為在橋梁測量時的位置是受過去幾個小時、幾天氣溫的溫度歷史影響。即使周全的考慮影響監(jiān)測測量結(jié)果的因素并且在每年的同一時期進(jìn)行測量，也需要相對較長的時間，我們才能弄清楚Lutrive橋在1988年進(jìn)行改造時額外橋梁后張[3,7,11]有沒有產(chǎn)生與兩者相同的影響。

圖1：Lutrive橋的長期撓度，與24小時內(nèi)撓度自動采集的數(shù)據(jù)，使得我們可以在一個可接受的成本上進(jìn)行方便地測量，因此非常可取。一個可能的解決方案研究，進(jìn)行了包括基于激光水準(zhǔn)，光纖傳感器和GPS定位，得出的結(jié)論是，只要可以確保它們的長期穩(wěn)定性，當(dāng)前類型的電子傾角儀，都適合于自動測量現(xiàn)有橋梁的旋轉(zhuǎn)量[8]。3.MENTUE道橋Mentue橋是單箱雙室箱梁橋，將銜接從洛桑到伯爾尼的未來A1高速公路。每片梁設(shè)計類似，擁有約565m的,整體長度和13.46m的寬度，設(shè)計承載兩行車線和一個應(yīng)急車道。橋梁跨越一兩側(cè)有陡峭山坡的深谷（圖2）。平衡懸臂橋梁施工設(shè)計是與另一橋梁方案比選的結(jié)果。100m高的混凝土橋墩用爬模施工方法完成后，平衡懸臂施工啟動（圖3）4.傾角儀從1995年開始，IBAP發(fā)起了一個研究項目，目的是調(diào)查利用傾角儀的測量系統(tǒng)的可行性。初步結(jié)果表明，傾角儀為結(jié)構(gòu)提供自動監(jiān)測提供了些許優(yōu)點。表1總結(jié)了本研究選擇的傾角儀的主要特性。

衡量結(jié)構(gòu)轉(zhuǎn)動的有趣屬性是，對于一個給定的最大撓度跨度比，最大旋轉(zhuǎn)基本上是獨立于它的靜態(tài)系統(tǒng)[8]。由于在永久荷載下，最大允許值約1/1000的長期撓度已經(jīng)被全世界普遍接受，就像這項研究中大跨度箱梁橋取得發(fā)展，同樣適用于其他橋梁，例如跨度較短橋梁和其他類型跨度區(qū)域。這是很重要的，因為需要檢測那些小跨度梁，他們構(gòu)成所有橋梁的大部分結(jié)構(gòu)。

表1傾角儀的主要特性特性描述絕對的測量相對于最初的位置，這種測量是絕對的。以防這種儀器的失敗，其他儀器提供的信息仍然是可以利用的。數(shù)據(jù)采集系統(tǒng)可容易聯(lián)接傾角儀是電子儀器，它所產(chǎn)生的電子信號可以被標(biāo)準(zhǔn)的數(shù)據(jù)采集系統(tǒng)很容易獲得。這項工程所使用的傾角儀包括一種工業(yè)網(wǎng)狀界面（RS485），其可以大大減少纜索的數(shù)量。檢測原理可以適用于各種橋梁本質(zhì)上，轉(zhuǎn)動的幅度是與靜定結(jié)構(gòu)或橋梁跨越的區(qū)域相互獨立的。因為儀器的可靠性，傾角儀可以被安置在可以伸手觸及的地方，因此可以適應(yīng)所有類型的跨越區(qū)域。高精度傾角儀的高精度使得極小變形的測量成為可能，比如那些只發(fā)生在幾分鐘之內(nèi)的的變形。安裝和操作簡單傾角儀是非常精巧的儀器，安裝只須很小的空間。我們挑選的傾角儀包括溫度自動補償。傳感器可以很容易安置并且能重復(fù)利用。成本盡管相對很高，與同類檢測系統(tǒng)相比，傾角儀很具有競爭力，并且安裝費相當(dāng)?shù)?。選定的傾角儀類型：偉倫Zerotronic±1°[9]。其準(zhǔn)確度為1microradian（μrad），相當(dāng)于一毫米每公里，是一個非常小的旋轉(zhuǎn)值。對于一個通常高度連續(xù)梁的中跨，1/20000的跨中撓度，將導(dǎo)致最大約150μrad的旋轉(zhuǎn)，或0.15毫弧度（mrad）。

電子儀器潛在的一個問題是他們的測量結(jié)果可能隨時間漂移。為量化和控制這個問題，設(shè)計了一種機(jī)械裝置，允許傾角為180°旋轉(zhuǎn)正是在一水平面上（圖4）。每個傾角儀的漂移可以通過比較獲得的初始值和旋轉(zhuǎn)位置與以前獲得值簡單地獲得。到目前為止，我們觀察到工程中使用的那種傾角儀的類型對漂流不是很敏感。5.曼圖橋的測試設(shè)備一些采用平衡懸臂施工的橋梁，在實際使用中的狀態(tài)并不理想/r